1. Field of the Invention
This invention relates to a system for purifying dye, particularly to a system for purifying dye capable of feeding continuously a purified dye which is suitable for preparation of a recording liquid suited for ink jet recording or writing implements (generally called as ink).
2. Description of the Prior Art
As the inks to be used for ink jet recording system, in which recording is performed by discharging the ink in the recording head through a discharging orifice by vibration with a piezoelectric vibrating element, etc., those containing various dyes or pigments dissolved or dispersed in a liquid medium comprising water or other organic solvents have been well known in the art. It is also known that similar inks can be used in writing implements such as felt pen, fountain pen, etc.
As an example of the basic constitution of such inks in general, there is a composition composed mainly of the three components of a water-soluble dye, water which is the solvent for the dye and a glycol which is the drying preventive.
Here, the water-soluble dye ordinarily contains inorganic salts such as sodium chloride, sodium sulfate, etc. and metal ions, especially heavy metal ions.
When an ink for recording is prepared with a dye containing such inorganic ions, the following inconvenience will be invited. That is, inorganic ions lower stability of the dye dissolved in the ink, whereby agglomeration or sedimentation of dye will be brought about. Also, in an ink jet recording head or a writing implement, if the liquid composition is changed by evaporation of the ink near the discharging orifice, precipitation of inorganic salts will be caused. Any of these may be a cause for clogging of the discharging orifice which should be avoided as the most undesirable trouble.
For the purpose of removing such troubles, it is necessary to control the inorganic ion concentration within a certain range in production of ink. This is indispensable when employing a commercially available dye in general containing inorganic ions as impurity for preparation of an ink for ink jet recording or an ink for writing implements.